EP2059378B1 - Device for filtering a thermoplastic polymer melt - Google Patents

Abstract

A description is given of a device (20) for filtering a thermoplastic polymer melt, comprising a housing (21), which is provided with an inlet channel (1) and an outlet channel for the polymer melt. The inlet channel is divided from the outlet channel by at least one cylindrical bore (3), extending perpendicularly in relation to the channels, for receiving at least one axially displaceable cylinder (4). The cylinder is provided with at least one through-opening for receiving at least one filter element. The filter element comprises a multiplicity of axially aligned candle filters (6). Seen in the direction of displacement of the cylinder, these candle filters have identical axial lengths within a first row and, perpendicularly to the direction of displacement of the cylinder, have such axial lengths in a second row that a minimized distance is formed between the head faces of the candle filters and the associated portion of the line of curvature of the bore.

Description

The present invention relates to a device for filtering a thermoplastic polymer melt having the features of the preamble of patent claim 1 and of patent claim 2, respectively.

Devices for filtering a thermoplastic melt are known in various embodiments, see for example the document DE 41 25 181 C1 , For example, describes the DE 40 12 404 C a corresponding device for filtering a thermoplastic resin melt, wherein the known device comprises a housing which is provided with an inlet channel for the plastic melt to be filtered and an outlet channel for the filtered plastic melt. Between the inlet channel and the outlet channel two perpendicular to the channels extending cylindrical bores are provided, which each serve to receive an axially displaceable bolt. During the Filtriervorganges the plastic melt aligned in each bolt passage opening with the inlet channel and the outlet channel, wherein within the passage opening a transversely to the flow direction arranged filter element is supported, which is equipped with a flat filter, which is also commonly referred to as a sieve.

An apparatus having the features of the preamble of claim 1 is known from DE 2 315 344 A known, wherein this known generic device differs from the device described above substantially in that the flat filter or the sieve in which from the DE 2 315 344 A known device is replaced by a plurality of filter cartridges, which are positioned in the axial direction of displacement of the bolt and perpendicular thereto in rows. The plastic melt to be filtered is supplied via the inlet channel, occurs thereafter in the bolt provided in the passage opening and is filtered by the filter cartridges positioned therein, wherein each filter candle is flowed through from the outside to the inside of the plastic melt, so that hereafter from the interior of the filter candle the then filtered plastic melt is discharged through the outlet channel and thus supplied as a filtered plastic melt to a downstream of the device, for example, arranged tool or nozzle.

In the previously described and from the DE 2 315 344 A known device all filter cartridges have an identical axial length, so that there is a considerable distance between the top surfaces of the filter cartridges and the associated portion of the line of curvature of the bore in the housing. This in turn has the disadvantage that here a considerable, not occupied by filter surfaces dead volume is formed, the experts believe this dead volume is necessary to ensure a proper and especially even arrival or flow through all filter cartridges.

The present invention has for its object to provide a device for filtering a thermoplastic resin melt available, in which a particularly uniform flow against all filter cartridges is ensured.

This object is achieved by a device with the characterizing features of claim 1 or by a device with the characterizing features of claim 2.

Advantageous developments of the device according to the invention are given in the dependent claims.

The inventive device for filtering a thermoplastic resin melt has a housing which is provided with an inlet channel for the plastic melt to be filtered and an outlet channel for the filtered plastic melt. The inlet channel is separated from the outlet channel in the device according to the invention by at least one perpendicular to these channels extending cylindrical bore, wherein within the cylindrical bore an axially displaceable pin is positioned. In this case, the bolt is arranged so precisely within the cylindrical bore that it prevents additional sealing means even with an axial displacement that pushes through between the outer wall of the bolt and the inner wall of the cylindrical bore in an undesirable manner plastic melt. The bolt is further provided with at least one passage opening for receiving at least one, consisting of a plurality of filter cartridges filter element, the filter cartridges are arranged in the direction of displacement of the bolt and perpendicular thereto in first rows and axially aligned in the flow direction of the plastic melt, such that the plastic melt to be filtered, the filter cartridges flow from the outside, so that the existing in the plastic melt dirt is filtered when passing the plastic melt through the jacket and possibly through the top surface of the filter cartridges, so that hereinafter leaves a filtered plastic melt from the filter element from the interior of the filter candle , In contrast to the generic type known device described above are seen in the inventive device in the direction of displacement of the bolt, the axial lengths of all filter cartridges a first row and furthermore seen perpendicular to the direction of displacement of the bolt, the axial lengths of all filter cartridges a second row to the line of curvature of the bore customized, that between the top surfaces of the filter cartridges and the associated portion of the line of curvature of the bore a minimized distance is formed. In other words, therefore, the tunnel-shaped space forming between the passage opening provided in the bolt and the corresponding section of the inner wall of the bore is filled to the maximum with filter cartridges by adapting the axial length of the filter cartridges in the device according to the invention, so that those previously described in the prior art Dead spaces in the device according to the invention do not exist or only to a considerably reduced extent.

Surprisingly, it was found that despite elimination or minimization of the dead space in the device according to the invention all filter cartridges flowed evenly and thus even in the course of use uniformly be filtered with dirt aggregates, so that accordingly in an exchange or regeneration of the filter cartridges in the inventive device no Filter candles could be found, which were more heavily occupied with dirt aggregates as of this adjacent filter cartridges. This in turn leads to the decisive advantage that in the device according to the invention not only the available filter surfaces in comparison to the generic type known device considerably, so in particular between 20% and 80%, is increased, so that accordingly in the required cleaning of the filter cartridges in the apparatus according to the invention compared to the conventionally known device a significantly extended operating time is made possible but that even if the device according to the invention replacement or regeneration of the filter cartridges due to contamination of the filter surfaces is required evenly contaminated filter cartridges are present. Therefore, the device according to the invention is characterized in particular by a longer operating time and evenly soiled filter candles, so that the inventive Device is particularly economical and to operate with significantly reduced personnel costs with uniform filtration performance and identical rheological behavior of the filtered plastic melt. Because of the previously described minimization of the dead space and the surprisingly uniform influx of all filter cartridges device prevents the invention particularly effective that in this dead space unwanted deposits, such as dirt aggregates or cracked plastic melt, take place, which in turn leads to a particularly trouble-free operation of the device according to the invention.

The above-described advantages of the device according to the invention occur in particular in large area filters, in which the bolt diameter between 400 mm and 800 mm, the number of candles between 30 filter cartridges and 80 filter cartridges, the axial lengths of the filter candle, depending on their position, between 150 mm and 600 mm , the filter candle diameter between 50 mm and 100 mm and, accordingly, the filter surfaces between 1.5 m ² and 15 m ² vary, which refers to a single filter element.

It should be noted that the filter cartridges used in the device according to the invention are preferably cylindrical or predominantly cylindrical filter cartridges, which in particular also have a uniform diameter, so that preferably a filter element is formed from a plurality of cylindrical filter cartridges with identical diameter. In special cases, however, it is also possible that for further optimization of the available filter surfaces such filter elements are provided in the device according to the invention, the filter cartridges group or rowwise identical and group or row by row have different diameters.

As already explained in the device according to the invention, the distance of the top surfaces of the filter cartridges and the associated portion of the line of curvature of the bore is minimized, in which case in particular the filter cartridges are arranged and aligned with respect to their axial length, that this distance between 2 mm and 0, 5 mm.

The device according to the invention provides that in this case all head surfaces of the filter cartridges is assigned a common end plate, which is provided with holes. Here, this end plate causes that specifically to be filtered plastic melt is distributed by means of the holes on the plurality of filter cartridges, in a development of this embodiment, then the common end plate is preferably provided with such holes, which have a different diameter. This prevents the formation of undesirable laminar flow areas when the filter cartridges flow against, which in turn homogenizes the supply of the plastic melt to be filtered to the plurality of filter cartridges. Furthermore, this common closure plate has the advantage that the dead space volume is thereby further reduced, which, as previously described, has significant rheological benefits and effectively prevents unwanted deposits. Furthermore, the end plate described above has the advantage that it can be checked whether each filter cartridge of a filter element is positioned at the right place. In order to check the correct positioning of all filter cartridges, it is possible to use an alternative end plate, which is only used as a control template at short notice when unladen filter cartridges are repositioned. After checking with the aid of this specially shaped control template it is removed, so that no end plate is provided during filtration.

In order to ensure a proper and secure positioning of the filter cartridges over a wide period of operation in the apparatus according to the invention, provides another embodiment of the device according to the invention, that in this case the filter cartridges are positioned on a perpendicular to the flow direction of the plastic melt support plate arranged with through openings for the Plastic melt is provided. By designing the support plate and / or by varying the size and / or the shape of the passage openings for the filtered plastic melt in the support plate, the rheological conditions can be influenced and optimized in the device according to the invention, which is particularly important when the device according to the invention as a large area filter , as quantified above, is formed.

In order to facilitate replacement of all filter cartridges of a filter element in the inventive device, a development of the embodiments described above provides that in this case the support plate is releasably connected to the end plate. In an exchange of such a filter element, the entire package of filter cartridges of a filter element is then removed after axial displacement of the bolt in an area outside the housing by means of a suitable lifting device or a corresponding pneumatic or hydraulic device of the passage opening and by a corresponding filter element, the filter cartridges not yet are loaded with dirt, exchanged, so that this development of the device according to the invention effectively reduces the required for a change of the filter elements downtime significantly. If, in addition, in this embodiment the retaining plate is assigned a locking element which cooperates with a corresponding counterpart which is positioned in the region of the passage opening, then this configuration allows particularly effective that such a configured filter element can always be properly positioned within the passage opening, so that it does not damage the bolt and / or the bore wall at an axial displacement.

In particular, the support plate is configured such that it has differently shaped fastening elements for the filter cartridges, so that it effectively prevents filter cartridges from being arranged at the wrong position on the support plate. This, of course, requires that the filter cartridges are designed foot side so that only certain filter cartridges can be fixed with a predetermined axial length at a certain location on the support plate.

In the device according to the invention each filter cartridge is provided with a, the top surface associated end member instead of the single end plate described above. Depending on the respective size of the passage opening and the axial length of the filter cartridges, this individual closure element can be designed individually from the point of view of influencing and optimizing the rheological conditions of the plastic melt fed and to be filtered, and furthermore serves to further reduce the unwanted dead space volume. From this point of view, the closure element is conical or cone-shaped, since a variation of the cone angle can bring about a desired influencing of the rheological conditions in a particularly simple manner.

With regard to the configuration of the passage opening provided in the bolt, which has an axial extent depending on the bolt strength and receives and supports the filter element, there are several possibilities.

Thus, the first possibility of the device according to the invention suggests that in this case the passage opening in the bolt has a polygonal cross section. In this case, the term polygon covers in particular convex polygons, wherein generally speaking the number of corners of the polygon depends on which diameter the bolt has and which diameter the respective filter cartridges to use, so that taking into account an optimized flow behavior, a maximum of filter cartridges within the polygon-shaped passage opening can be arranged. In particular, the passage opening in this first possibility in the cross section of the passage opening and thus seen in the flow direction of the thermoplastic melt to be filtered seen a quadrangular to decagonal, preferably convex shape. To clarify, it should be noted that the term polygon not only designates polygons which contain corners in a strictly mathematical sense, but also covers those embodiments which are to be described as polygon-like and thus have no corners in the strict mathematical sense but correspondingly rounded corners.

Due to the fact that the passage opening provided in the bolt has, depending on the respective bolt diameter, an axial length adapted to the bolt diameter such that it extends completely through the bolt, the above-described polygonal passage opening can be designed to be continuous polygon over its entire axial length. In a particularly suitable from a flow point of development of the first possibility described above, however, the polygonal passage opening is designed such that it is polygonal in a first, the inlet channel facing portion and that downstream of the filter element, a second portion of the passage opening adjoins, in which polygonal passage opening then opens into a round passage opening. In this development, the thermoplastic melt to be filtered is over a cross section fed round inlet channel, the ends opens into the polygonal passage opening, takes place in this junction area a turbulence of the flowing plastic melt, with the result that here forms a turbulent flow, which ensures a particularly uniform supply of all filter cartridges. Downstream of the filter element then causes the previously described transition from the polygonal shape to the round shape in the region of the second section that the flow of the now filtered plastic melt is calmed, so that arranged over the outlet channel a uniform and continuous flow of plastic melt after the filtering device Tool or the nozzle is supplied.

This previously mentioned advantage occurs in particular when the diameter of the round passage opening provided in the second section is identical to the diameter of the junction area of the outlet channel.

In a particularly suitable development of the first option described above, the polygonal passage opening is formed in the cross section as a regular hexagon. This development is convincing by the fact that due to the design of the cross section of the passage opening here a maximum of filter cartridges can be arranged, in spite of this maximum loading with filter cartridges each filter cartridge is acted upon with an optimum plastic melt stream, with the result that after expiration of a corresponding Operating time all filter cartridges are evenly loaded with filtered contamination. By way of clarification, the term regular hexagon not only covers such convex hexagons in which the angles and the side lengths are identical, but also those hexagons which have identical angles as well as four identically long sides and furthermore additionally two identical sides, where the length of the four sides is different from the length of the two sides, like this will be described below in an embodiment.

The second possibility of the device according to the invention suggests that in this case the passage opening, which is provided in the bolt, is designed as a round and thus cylindrical passage opening.

If, on the other hand, the number of filter cartridges provided in a filter element is to be increased for a given bolt diameter in comparison to the second option described above, the third possibility provides that the passage opening in the bolt is designed to be oval, while the fourth embodiment provides the shape of the passage opening in that in this case this passage opening is configured from two, partially overlapping, round passages. It should be further noted that the above-described four ways of designing the differently shaped cross-section through openings according to how the degree of contamination of the plastic melt to be filtered is and in particular, which rheological problems prepares each to be filtered plastic melt.

A development of the embodiments described above, in which the passage opening in the bolt is configured oval or two, partially overlapping round passages is formed, provides that these passages in the bolt over the cross section of the bolt seen in a first section accordingly oval or out two partially overlapping round passage openings is formed and that this is followed downstream of the filter element, a second portion of the passage opening, which is designed as a round channel. The diameter of this round channel is in particular to the diameter of the adjacent thereto area adapted to the outlet channel, so that seamlessly provided in the bolt portion channel opens into the corresponding region of the outlet channel.

Earlier it was stated that the filter element must be replaced after a predetermined or individually determined operating time. In order to effect this replacement, there is initially the possibility in the device according to the invention that the device is deactivated by an axial displacement of the bolt, so that no plastic melt is filtered at this time and the filter element has been brought into a position in which it is accessible from the outside. Accordingly, this embodiment of the device according to the invention comprises a housing with a single inlet channel, a single outlet channel, a single cylindrical bore for axially displaceable mounting of a single bolt, wherein the bolt in turn is provided with a single passage opening for receiving a single filter element.

However, it is particularly advantageous if the at least one cylindrical bolt is provided with two axially spaced-apart passage openings each for receiving a filter element, wherein in a first position of the bolt, the filter candles are flowed through by both filter elements with the plastic melt to be filtered and in a second position of the bolt, the filter cartridges are traversed by a filter element with the plastic melt to be filtered, while at the same time the filter cartridges of the other filter element is in a position outside the housing of the device, so that this filter element can then be exchanged for such a filter element, with fresh filter candles, ie such filter cartridges, which were not yet involved in the filtration process, is provided. In order to achieve such a second position, it is necessary that the Move bolt from the first position to the second position axially.

A variation of the previously described embodiment of the device according to the invention provides that in this case in the first position of the bolt, both filter elements are not in the filtration position but only a single filter element, while the other filter element is not acted upon by the plastic melt. Rather, this filter element is in a position in which it is located outside the housing. This variant is used in particular when the particular plastic melt to be filtered in particular sensitive to pressure fluctuations and / or increased pressure.

In another embodiment of the device according to the invention this has at least two, arranged within a housing and axially displaceable thereto bolts, which are each provided with at least two, with axial spacing from each other arranged filter elements. In a first position of the two bolts, the filter cartridges of all filter elements are flowed through by the plastic melt to be filtered. In a second position of one of the two bolts is a filter element in a position outside the housing of the device, so that it is accordingly replaced with a fresh filter element, while at the same time the filter cartridges of the other remaining filter elements are flowed through by the plastic melt to be filtered. In order to achieve the first or second position of the bolts, they are arranged axially displaceable. With this embodiment of the device according to the invention, it is possible to maintain 75% of the maximum filtration capacity even when a filter element is outside the housing and thus this filter element is replaced by a fresh filter element.

The above-described embodiments of the device according to the invention provide that in this case the filter elements are replaced when the filter cartridges are loaded with soil aggregates and thus an exchange is required.

In a fundamentally different embodiment of the device according to the invention, this comprises at least one cylindrical pin, which is provided with two, with axial spacing from each other arranged passage openings each for receiving a filter element. In a first position of the bolt, the filter cartridges are flowed through by both filter elements with the plastic melt to be filtered. By an axial displacement of the bolt is then transferred to a second position as soon as it is established that the filter cartridges of a filter element are almost completely loaded with dirt aggregates, wherein in the second position of the at least one bolt, the filter cartridges of a filter element to be filtered with the melted plastic to be flowed through while at the same time the filter cartridges of the other filter element backwashed with filtered plastic melt, ie flows through the opposite direction to the filtering, so that then originally filtered plastic melt laden with dirt aggregates through this backwashing and be discharged from the housing via a discharge channel open to the atmosphere. This discharge channel is of course closed in the first position of the bolt and open to the atmosphere only in the second position of the bolt. As in the previously described embodiments, the first position and the second position and vice versa are brought about by an axial displacement of the bolt.

By way of clarification, it should be noted that the term plastic melt used in the present description particularly includes a polypropylene, polyethylene, high-pressure polypropylene, low-pressure polyethylene, linear low-pressure polyethylene, polystyrene, Polyamide, alkyl butadiene styrene (ABS), polyester, polyoxymethylene (POM), polyacrylate, polymethylmethacrylate (PMMA) and polyvinyl chloride melt. Furthermore, it should be clarified that all terms used in the singular in the present description not only includes the one term, but that also includes any number of these terms. It should also be noted that all terms associated with "and / or" are to be construed both as additive and as an alternative, this statement also being valid if, for a list of more than two terms, only the last two terms with "and / or "are connected, so that in this type of enumeration all terms or only a part of the concepts are additive or alternatively linked together. The terms upstream and downstream always refer to the flow direction of the plastic melt to be filtered. Furthermore, it should be noted that the term "row" used in the present description not only means a linear succession of the filter cartridges but can also express that this "row of filter cartridges" curved or arcuate, the shape of this course is particularly dependent on according to which pattern the filter cartridges are arranged on the support plate. It is further to be understood that the filter cartridges of a filter element are arranged not only in a single first row and in a single second row, but that the filter cartridges are positioned in a plurality of successive first rows and in a plurality of consecutive second rows as well in particular also shown in the drawing.

Figur 1

eine schematische Darstellung einer Vorrichtung zum Filtrieren einer thermoplastischen Kunststoffschmelze;

Figur 2

eine schematische perspektivische Teilansicht des Bol- zens mit der im Bolzen vorgesehenen Durchtrittsöffnung und dem dort angeordneten Filterelement;

Figur 3

eine perspektivische Teilansicht in Blickrichtung der Linie A-B in Figur 2;

Figur 4

eine perspektivische Teilansicht in Blickrichtung der Linie C-D in Figur 2;

Figur 5

eine schematische Schnittansicht des Bolzens gemäß der Linie A-B in Figur 7 mit teilweise herausgebrochener Wandung mit der im Bolzen vorgesehenen Durchtrittsöff- nung und dem dort angeordneten Filterelement gemäß der Erfindung;

Figur 6

eine perspektivische Teilansicht längs der Linie A-B in Figur 7;

Figur 7

eine perspektivische Teilansicht der Erfindung;

Figur 8

eine Explosionszeichnung der im Bolzen vorgesehenen Durchtrittsöffnung und dem dort angeordneten Filter- element gemäß der Erfindung;

Figur 9

eine schematische perspektivische Teilansicht des Bol- zens mit der im Bolzen vorgesehenen Durchtrittsöffnung und dem dort angeordneten Filterelement ; und

Figur 10

eine schematische perspektivische Ansicht des Bolzens mit der im Bolzen vorgesehenen Durchtrittsöffnung und dem dort angeordneten Filterelement .

The device according to the invention is explained in more detail below with reference to five exemplary embodiments in conjunction with the drawing. Show it:

FIG. 1

a schematic representation of an apparatus for filtering a thermoplastic resin melt;

FIG. 2

a schematic perspective partial view of the bolt with the bolt provided in the passage opening and the filter element arranged there;

FIG. 3

a partial perspective view in the direction of the line AB in FIG. 2 ;

FIG. 4

a partial perspective view in the direction of the line CD in FIG. 2 ;

FIG. 5

a schematic sectional view of the bolt according to the line AB in FIG. 7 with partially broken wall with the passage opening provided in the bolt and the filter element arranged there according to the invention;

FIG. 6

a partial perspective view along the line AB in FIG. 7 ;

FIG. 7

a partial perspective view of the invention;

FIG. 8

an exploded view of the provided in the bolt passage and the filter element arranged there according to the invention;

FIG. 9

a schematic perspective partial view of the bolt with the bolt provided in the passage opening and the filter element arranged there; and

FIG. 10

a schematic perspective view of the bolt with the bolt provided in the passage opening and the filter element arranged there.

In the FIGS. 1 to 10 the same parts are provided with the same reference numerals.

In FIG. 1 schematically a device (indicated generally by 20) for filtering a thermoplastic melt, wherein the device 20 comprises a housing 21. In the illustrated example of the device, the housing 21 of the device 20 is provided with two cylindrical bores 3, wherein the cylindrical bores 3 an upper pin 4 and a lower pin 4a axially displaceable in the direction of arrow 22 and vice versa store it. In order to effect this axial displacement of the bolts 4 and 4a, hydraulic elements 23 are assigned to the two bolts 4 and 4a, respectively. The upper pin 4 and the lower pin 4a are of identical design and have at least one passage opening 5 extending in the flow direction (arrow 28) of the plastic melt to be filtered, as can be seen in the upper pin 4. This passage opening 5 receives in each case a filter element, which in various embodiments in the FIGS. 2 to 9 is shown in detail. Seen in the direction of flow of the molten plastic to be filtered, this plastic melt passes through an inlet channel 1 into the housing 21 of the device 20, from there into the passage opening 5, which is aligned with the inlet channel 1 during filtration, is filtered by the arranged in the passage opening 5 filter element and reaches downstream of the filter element in the outlet channel (not visible), which in turn is aligned during filtration with the inlet channel and the passage opening in turn. Downstream of the outlet channel, a tool or nozzle, not shown, is positioned, which is supplied with filtered plastic melt as continuously as possible. As in FIG. 1 It can be seen hinted, the inlet channel 1 is divided into two sub-channels, so that the inlet channel near the front of the housing 21 divides, so as a partial flow of the plastic melt to be filtered to the lower pin 4a and another partial flow of the plastic melt to be filtered to guide upper bolt 4. Accordingly, the outlet channel, not shown, is also divided and terminates in a common outlet channel.

At the in FIG. 1 shown embodiment, the lower bolt 4a is in the working position (filtration position), while the upper pin 4 is shown in a position in which the passage opening 5 is freely accessible from the outside, so that here an exchange of the loaded with dirt particles filter element against an unloaded filter element can be done.

The cylindrical bores 3 in the housing 21 are adapted to the diameter of the bolts 4 and 4a, that even with an axial displacement of the bolt in the direction of arrow 22 no leakage occurs and thus no plastic melt can escape undesirable here.

In the FIGS. 2 to 4 an embodiment is shown as a partial view showing in detail how in the device, the filter cartridges 6 of the total designated 7 filter element are formed and arranged.

Like from the FIGS. 2 to 4 can be seen, the filter element 7 has a plurality of filter cartridges 6, which of a are held transversely to the flow direction of the plastic melt positioned round support plate 14 and arranged respectively in such first rows 9 and second rows 9a, which, depending on the figure, in accordance with FIGS. 2 and 3 arcuately curved and according to FIG. 4 apparently linearly oriented. To clarify it is to be noted that with the FIGS. 2 to 9 only one first row 9 and one second row 9a are shown by way of example.

Seen in the direction 22 of the bolt (only at Figures 2 and 9 the axial lengths of all the filter cartridges 6 of the first row 9 are identically large, while the axial lengths of a second row 9a of the filter cartridges 6 are adapted perpendicular to the direction of displacement of the bolt 4 (seen in the direction of arrow 29) to the line of curvature of the bore 3, that between the top surfaces 11 of the filter cartridges 6 and the associated portion of the line of curvature of the bore 3 ( FIG. 1 ) is formed only a minimized distance. The entire surface of the support plate 14 is occupied with filter cartridges 6 aligned in successive first rows 9 and second rows 9a. Due to the tight adaptation of the diameter of the bolt 4 to the bore 3 in the housing 21, the line of curvature of the bore 3 is approximately identical to the outer wall of the bolt 4, so that the passage opening 5 in the bolt while maintaining a minimum dead zone completely with filter cartridges upstream of the Support plate 14 is filled.

In the FIGS. 5 to 7 the invention according to claim 1 is shown as a partial view, which shows in detail how the filter cartridges 6 of the total designated 7 filter element are formed and arranged in the device. In this case, this second embodiment differs from the one previously described in connection with FIGS FIGS. 2 to 4 described first embodiment in that in the second embodiment according to the FIGS. 5 to 7 each head surface 11 of the filter cartridges 6 with a closure element 15 is provided, so that in this second embodiment, this conically shaped closure element 15 on the one hand performs a rheological guiding function for the plastic melt to be filtered and on the other hand in the sense of the above description forms a head surface of the filter cartridges, which minimizes the distance to the associated portion of the line of curvature of the bore and thus reduces the dead zones in volume above the top surfaces of the filter cartridges.

In the FIG. 8 the invention according to claim 2 is shown as an exploded view showing in detail how in the device, the filter cartridges 6 of the total designated 7 filter element are formed and arranged. Here, this third embodiment differs from the previously described in connection with FIGS. 5 to 7 described in the second embodiment in that in the third embodiment according to the FIG. 8 provided in the second embodiment, individual closure elements 15 which are assigned to each filter cartridge 6 individually, are replaced by a common end plate 12 which is interspersed with a plurality of holes 13. Like the separate picture (top picture of the FIG. 8 ) of the end plate 12 can be seen, distributed over the surface holes 13 are provided with different diameters, so that thereby individually the rheological behavior of the plastic melt to be filtered can be controlled. Furthermore, it can be clearly seen that the end plate 12 is curved and has a tunnel-shaped curvature, so as to tightly adapt to the first rows 9 and the second rows 9a of the filter cartridges 6 and thus to reduce the dead volume while optimizing the filter surfaces the support plate 14 on a radially inwardly projecting annular element 27 which is provided within the passage opening 5, supported, as is the case with the embodiments described above. Thus, the surface of the end plate 12 forms the top surfaces of the filter cartridges in the sense of above description. If desired, the end plate 12 may be releasably connected to the support plate 14 with the inclusion of the filter cartridges 6, so as to be able to remove the filter element 7 as a whole easier when changing.

Basically, it should be noted in this connection that, if necessary, in all the embodiments described above, the filter cartridges 6 can be releasably connected to the support plate 14, so for example by appropriate threaded or bayonet connections.

In the FIG. 9 an embodiment is shown as a partial view showing in detail how in the device, the filter cartridges 6 of the total designated 7 filter element are formed and arranged. Here, this fourth embodiment differs from that previously described in connection with FIGS FIGS. 2 to 4 described in the first embodiment in that in the fourth embodiment according to the FIG. 9 the passage opening 5 in the pin 4 is not round but oval, so that in this way the number of filter cartridges 6 and thus also the entire filter surfaces is increased or become.

As also from the FIG. 9 can be seen, the filter element 7 has a plurality of filter cartridges 6, which are supported by a transversely positioned to the flow direction of the plastic melt oval support plate 14 and arranged in each case in such first rows 9 and second rows 9a, as previously described. To clarify it is to be noted that in the FIG. 9 only one first row 9 and one second 9a each are shown by way of example.

In the direction of displacement 22 of the bolt, the axial lengths of all filter cartridges 6 of the first row 9 are identical, while seen perpendicularly (expressed by arrow direction 29) to the displacement direction 22 of the bolt 4, the axial lengths of the second row 9a of the filter cartridges 6 to the line of curvature of the bore 3 (FIG. FIG. 1 ) are adapted so that between the top surfaces 11 of the filter cartridges 6 and the associated portion of the line of curvature of the bore 3 ( FIG. 1 ) is formed only a minimized distance. The entire surface of the support plate 14 is occupied with filter cartridges 6 aligned in successive first rows 9 and second rows 9a. Due to the tight adaptation of the diameter of the bolt 4 to the bore 3 in the housing 21, the line of curvature of the bore 3 is approximately identical to the outer wall of the bolt 4, so that the passage opening 5 in the bolt while maintaining a minimum dead zone completely with filter cartridges upstream of the Support plate 14 is filled. Downstream of the filter element 7 and in particular downstream of the support plate 14, the oval passage opening 5 opens into a channel 30, wherein the channel 30 has a round diameter which is identical to the diameter of the round outlet channel.

The FIG. 10 illustrates an embodiment of a bolt as a perspective view, which shows in detail how in the device, the filter cartridges 6 of the generally designated 7 filter element are formed and arranged. In this case, this fifth embodiment differs from the previously mentioned in connection with FIGS. 2 to 4 described in the first embodiment in that in the fifth embodiment according to the FIG. 10 the passage opening 5 in the bolt 4 is not round but hexagonal, so that in this way the number of filter cartridges 6 and thus also the entire filter surfaces is or will be increased.

As also from the FIG. 10 can be seen, the filter element 7 on a plurality of filter cartridges 6. An unrecognizable hexagonal mounting plate, transverse to the flow direction the plastic melt is positioned within the bolt 4, supports the predominantly cylindrical filter cartridges 6. These filter cartridges 6 are each arranged in such first rows 9 and second rows 9a, as they have already been described. To clarify it is to be noted that in the FIG. 10 only one first row 9 and one second 9a each are shown by way of example.

In the direction of displacement 22 of the bolt, the axial lengths of all filter cartridges 6 of the first row 9 are identically large, while seen perpendicularly (expressed by arrow 29) to the direction 22 of the bolt 4, the axial lengths of the second row 9a of the filter cartridges 6 to the line of curvature of the bore 3 ( FIG. 1 ) are adapted so that between the top surfaces 11 of the filter cartridges 6 and the associated portion of the line of curvature of the bore 3 ( FIG. 1 ) is formed only a minimized distance. Due to the tight adaptation of the diameter of the bolt 4 to the bore 3 in the housing 21, the curvature of the bore 3 is approximately identical to the outer wall of the bolt 4, so that the hexagonal passage opening 5 in the bolt while maintaining a minimum dead zone completely upstream with filter cartridges the support plate is filled. Downstream of the filter element 7 and in particular downstream of the support plate, the hexagonal passage opening 5 in the region of the second section opens into a round cross-section (not shown), wherein the diameter of this round passage opening region is identical to the diameter of the likewise round outlet channel. This means that the passage opening seen over its axial length has a hexagonal first section facing the inlet channel and also has a hexagonal cross-section downstream of the mounting plate, which, however, opens within the bolt in a round cross-section, said passage opening area was referred to above as the second section , With respect to the configuration of the cross section of the passage opening in FIG. 10 As shown above, it should be noted that this is, as already repeatedly mentioned above, in the first section and partly also in the second section is a hexagon. This hexagon is a regular convex hexagon in which all angles are identical. The length of the four sides a to d of this hexagon are also identical, while the side e and the in FIG. 10 unrecognizable, aligned parallel thereto side are also identically long, but longer than the four sides a to d. Therefore, you can see the cross-sectional shape seen in the direction of displacement of the bolt as elongated hexagon.

Claims (18)

1. A device for filtering a thermoplastic melt with a housing that is provided with an inlet channel for the plastic melt and with an outlet channel for the plastic melt, wherein the inlet channel is separated from the outlet channel by at least one cylindrical bore running perpendicularly to the channels for accommodating at least one axially displaceable bolt and the bolt is provided with at least one passage opening for accommodating at least one filter element consisting of a multiplicity of filter candles, which in displacement direction of the bolt and vertically thereto are arranged in rows and which in flow direction of the plastic melt are orientated axially, wherein seen in displacement direction of the bolt the axial lengths of all filter candles of a first row are identical and seen vertically to the displacement direction of the bolt the axial lengths of all filter candles of a second row are adapted to the curvature line of the bore in such a manner that between the head surfaces of the filter candles and the associated section of the curvature line of the bore a minimized spacing is formed, characterised in that all head surfaces (11) of the filter candles (6) are assigned a common end plate (12) which is provided with bores (13).
2. A device for filtering a thermoplastic melt with a housing that is provided with an inlet channel for the plastic melt and with an outlet channel for the plastic melt, wherein the inlet channel is separated from the outlet channel by at least one cylindrical bore running perpendicularly to the channels for accommodating at least one axially displaceable bolt and the bolt is provided with at least one passage opening for accommodating at least one filter element consisting of a multiplicity of filter candles, which in displacement direction of the bolt and vertically thereto are arranged in rows and which in flow direction of the plastic melt are orientated axially, wherein seen in displacement direction of the bolt the axial lengths of all filter candles of a first row are identical and seen vertically to the displacement direction of the bolt the axial lengths of all filter candles of a second row are adapted to the curvature line of the bore in such a manner that between the head surfaces of the filter candles and the associated section of the curvature line of the bore a minimized spacing is formed, characterised in that each filter candle (6) is provided with a conical or cone-like element assigned to the head surface.
3. The device according to claim 1 or 2, characterised in that the head surfaces (11) of the filter candles (6) are arranged with a spacing of 2 mm to 0,5 mm to the corresponding section of the curvature line of the bore (3).
4. The device according to claim 1 or 3, characterised in that the bores (13) have different diameters.
5. The device according to any one of the preceding claims, characterised in that the filter candles (6) are positioned on a holding plate (14) arranged perpendicularly to the flow direction of the plastic melt, which is provided with passage orifices for the plastic melt.
6. The device according to claim 1 and 5, characterised in that the holding plate (14) is releasably connected to the end plate (12).
7. The device according to any one of the preceding claims, characterised in that the passage opening (5) in the bolt (4) has a polygonal, more preferably a quadrangular to decagonal cross section.
8. The device according to claim 7, characterised in that the passage opening (5) in the bolt (4) is formed polygonally in a first section facing the inlet channel (1) and that down stream of the filter element (7) a second section of the passage opening (5) follows in which this polygonal passage opening terminates in a round passage opening.
9. The device according to claim 8, characterised in that the diameter of the round passage opening provided in the second section is identical to the diameter of the termination region of the outlet channel (2).
10. The device according any one of the claims 7 to 9, characterised in that the polygonal passage opening is designed as a regular hexagon in cross section.
11. The device according to any one of the claims 1 to 6, characterised in that the passage opening (5) in the bolt (4) is designed round.
12. The device according to any one of the claims 1 to 6, characterised in that the passage opening (5) in the bolt (4) is designed oval.
13. The device according to any one of the claims 1 to 6 or 11, characterised in that the passage opening (5) in the bolt (4) is designed as two round passage openings partly covering each other.
14. The device according to claim 12 or 13, characterised in that the passage opening (5) in the bolt (4) in a first section is designed oval or of two round passage openings (5) partly covering each other and that downstream of the filter element (7) a second section of the passage opening (5) follows which is formed of a round channel (30).
15. The device according to any one of the preceding claims, characterised in that the housing (21) comprises a single inlet channel (1), a single outlet channel, a single cylindrical bore (3) for the axially displaceable mounting of a single bolt (4; 4a), wherein the bolt has a single passage opening (5) for accommodating a single filter element (7).
16. The device according to any one of the claims 1 to 14, characterised in that the cylindrical bolt (4; 4a) is provided with two passage openings arranged with axial spacing to each other each for accommodating a filter element (7), wherein in a fist position of the bolt the plastic melt to be filtered flows through the filter candles (6) of both filter elements (7) and in a second position of the bolt (4, 4a) the plastic melt to be filtered flows through the filter candles (6) of one filter element (7), while the filter candles (6) of the other filter element (7) simultaneously are located in a position outside the housing (21) of the device (20), and that the bolt (4, 4a) can be axially displaced from the first position into the second position and vice versa.
17. The device according to any one of the claims 1 to 14, characterised in that the device (20) comprises at least two bolts (4, 4a) arranged within a housing (21) and displaceable axially thereto, each of which is provided with at least two filter elements (7) arranged with axial spacing from each other, wherein in a first position of the bolt (4, 4a) the plastic melt to be filtered flows through the filter candles (6) of all filter elements (7) and in a second position of the one of the two bolts at least one filter element (7) is located in a position outside the housing (21) of the device (20), while the plastic melt to be filtered simultaneously flows through the filter candles (6) of the other remaining filter elements (7), and that the bolts (4, 4a) can be axially displaced from the first position into the second position and vice versa.
18. The device according to any one of the claims 1 to 14, characterised in that the at least one cylindrical bolt (4, 4a) is provided with two passage openings (5) arranged with axial spacing from each other each for accommodating a filter element (7), wherein in a first position of the bolt (4, 4a), the plastic melt to be filtered flows through the filter candles (6) of both filter elements (7) and in a second position of the at least one bolt (4, 4a) the plastic melt to be filtered flows through the filter candles (6) of the one filter elements (7), while the filter candles (6) of the other filter element (7) are simultaneously backflushed with filtered plastic melt, in that the housing (21) is assigned a discharge channel open to the atmosphere, which in the first position of the bolt (4, 4a) is closed and in the second position of the bolt is opened to the atmosphere, and in that the bolt can be axially displaced from the first position into the second position and vice versa.

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